/*
 * tsh - A tiny shell program with job control
 *
 * <Put your name and login ID here>
 */

#define _XOPEN_SOURCE 700
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <stdarg.h>
/* Misc manifest constants */
#define MAXLINE 1024   /* max line size */
#define MAXARGS 128    /* max args on a command line */
#define MAXJOBS 16     /* max jobs at any point in time */
#define MAXJID 1 << 16 /* max job ID */

/* Job states */
#define UNDEF 0 /* undefined */
#define FG 1    /* running in foreground */
#define BG 2    /* running in background */
#define ST 3    /* stopped */

/*
 * Jobs states: FG (foreground), BG (background), ST (stopped)
 * Job state transitions and enabling actions:
 *     FG -> ST  : ctrl-z
 *     ST -> FG  : fg command
 *     ST -> BG  : bg command
 *     BG -> FG  : fg command
 * At most 1 job can be in the FG state.
 */

/* Global variables */
extern char **environ;   /* defined in libc */
char prompt[] = "tsh> "; /* command line prompt (DO NOT CHANGE) */
int verbose = 0;         /* if true, print additional output */
int nextjid = 1;         /* next job ID to allocate */
char sbuf[MAXLINE];      /* for composing sprintf messages */

struct job_t
{                          /* The job struct */
    pid_t pid;             /* job PID */
    int jid;               /* job ID [1, 2, ...] */
    int state;             /* UNDEF, BG, FG, or ST */
    char cmdline[MAXLINE]; /* command line */
};
struct job_t jobs[MAXJOBS]; /* The job list */
/* End global variables */

/* Function prototypes */

/* Here are the functions that you will implement */
void eval(char *cmdline);
int builtin_cmd(char **argv);
void do_bgfg(char **argv);
void waitfg(pid_t pid);
void signal_safe_print(const char *format, ...)
{
    va_list args;
    char *ptr;
    char buffer[65536]; // 确保这个缓冲区足够大以容纳你的输出
    int written;

    // 格式化字符串到缓冲区
    va_start(args, format);
    vsnprintf(buffer, sizeof(buffer), format, args);
    va_end(args);

    // 写入到标准错误
    written = write(STDERR_FILENO, buffer, strlen(buffer));
    if (written < 0)
    {
        puts("Write error\n");
    }
}
void sigchld_handler(int sig);
void sigtstp_handler(int sig);
void sigint_handler(int sig);

/* Here are helper routines that we've provided for you */
int parseline(const char *cmdline, char **argv);
void sigquit_handler(int sig);

void clearjob(struct job_t *job);
void initjobs(struct job_t *jobs);
int maxjid(struct job_t *jobs);
int addjob(struct job_t *jobs, pid_t pid, int state, char *cmdline);
int deletejob(struct job_t *jobs, pid_t pid);
pid_t fgpid(struct job_t *jobs);
struct job_t *getjobpid(struct job_t *jobs, pid_t pid);
struct job_t *getjobjid(struct job_t *jobs, int jid);
int pid2jid(pid_t pid);
void listjobs(struct job_t *jobs);

void usage(void);
void unix_error(char *msg);
void app_error(char *msg);
typedef void handler_t(int);
handler_t *Signal(int signum, handler_t *handler);

/*
 * main - The shell's main routine
 */
int main(int argc, char **argv)
{
    char c;
    char cmdline[MAXLINE];
    int emit_prompt = 1; /* emit prompt (default) */

    /* Redirect stderr to stdout (so that driver will get all output
     * on the pipe connected to stdout) */
    dup2(1, 2);

    /* Parse the command line */
    while ((c = getopt(argc, argv, "hvp")) != EOF)
    {
        switch (c)
        {
        case 'h': /* print help message */
            usage();
            break;
        case 'v': /* emit additional diagnostic info */
            verbose = 1;
            break;
        case 'p':            /* don't print a prompt */
            emit_prompt = 0; /* handy for automatic testing */
            break;
        default:
            usage();
        }
    }

    /* Install the signal handlers */

    /* These are the ones you will need to implement */
    Signal(SIGINT, sigint_handler);   /* ctrl-c */
    Signal(SIGTSTP, sigtstp_handler); /* ctrl-z */
    Signal(SIGCHLD, sigchld_handler); /* Terminated or stopped child */

    /* This one provides a clean way to kill the shell */
    Signal(SIGQUIT, sigquit_handler);

    /* Initialize the job list */
    initjobs(jobs);

    /* Execute the shell's read/eval loop */
    while (1)
    {

        /* Read command line */
        if (emit_prompt)
        {
            signal_safe_print("%s", prompt);
            fflush(stdout);
        }
        if ((fgets(cmdline, MAXLINE, stdin) == NULL) && ferror(stdin))
            app_error("fgets error");
        if (feof(stdin))
        { /* End of file (ctrl-d) */
            fflush(stdout);
            exit(0);
        }

        /* Evaluate the command line */
        eval(cmdline);
        fflush(stdout);
        fflush(stdout);
    }

    exit(0); /* control never reaches here */
}

/*
 * eval - Evaluate the command line that the user has just typed in
 *
 * If the user has requested a built-in command (quit, jobs, bg or fg)
 * then execute it immediately. Otherwise, fork a child process and
 * run the job in the context of the child. If the job is running in
 * the foreground, wait for it to terminate and then return.  Note:
 * each child process must have a unique process group ID so that our
 * background children don't receive SIGINT (SIGTSTP) from the kernel
 * when we type ctrl-c (ctrl-z) at the keyboard.
 */
void eval(char *cmdline)
{
    char *argv[MAXARGS]; // 解析命令行数组
    int state = UNDEF;   // 工作状态，FG或BG
    sigset_t Signalset;
    pid_t pid; // 进程id

    if (parseline(cmdline, argv) == 1) // 解析命令行，返回给argv数组
        state = BG;
    else
        state = FG;
    if (argv[0] == NULL) // 检查命令是否为空，空目标直接返回
        return;

    if (!builtin_cmd(argv)) // 非builtin命令，划分线程
    {
        // 阻塞SIGCHLD信号，等待记录子进程生成情况后再开放信号执行子进程。
        if (sigemptyset(&Signalset) < 0)
            unix_error("sigemptyset error");
        if (sigaddset(&Signalset, SIGINT) < 0 || sigaddset(&Signalset, SIGTSTP) < 0 || sigaddset(&Signalset, SIGCHLD) < 0)
            unix_error("sigaddset error");
        if (sigprocmask(SIG_BLOCK, &Signalset, NULL) < 0)
            unix_error("sigprocmask error");
        // 子进程创建以及检查
        if ((pid = fork()) < 0)
            unix_error("fork error");
        else if (pid == 0) // fork创建子进程
        {
            if (sigprocmask(SIG_UNBLOCK, &Signalset, NULL) < 0) // 解除阻塞
                unix_error("sigprocmask error");
            if (setpgid(0, 0) < 0) // 设置子进程id（实际上并没有分进程组，因为一人一组）
                unix_error("setpgid error");

            if (execve(argv[0], argv, environ) < 0)
            {
                signal_safe_print("%s: command not found\n", argv[0]);
                exit(0);
            }
        }

        // 父进程控制流
        addjob(jobs, pid, state, cmdline); // 将当前进程添加进jobs中，参数为当前进程pid,state,cmdline

        // 恢复受阻塞的信号,子进程运行。
        if (sigprocmask(SIG_UNBLOCK, &Signalset, NULL) < 0)
            unix_error("sigprocmask error");

        // 判断子进程类型并做处理
        if (state == FG)
            waitfg(pid); // 等待子进程的前台作业完成
        else
            signal_safe_print("[%d] (%d) %s", pid2jid(pid), pid, cmdline); // 将进程id映射到job id
    }
    return;
}

/*
 * parseline - Parse the command line and build the argv array.
 *
 * Characters enclosed in single quotes are treated as a single
 * argument.  Return true if the user has requested a BG job, false if
 * the user has requested a FG job.
 */
int parseline(const char *cmdline, char **argv)
{
    static char array[MAXLINE]; /* holds local copy of command line */
    char *buf = array;          /* ptr that traverses command line */
    char *delim;                /* points to first space delimiter */
    int argc;                   /* number of args */
    int bg;                     /* background job? */

    strcpy(buf, cmdline);
    buf[strlen(buf) - 1] = ' ';   /* replace trailing '\n' with space */
    while (*buf && (*buf == ' ')) /* ignore leading spaces */
        buf++;

    /* Build the argv list */
    argc = 0;
    if (*buf == '\'')
    {
        buf++;
        delim = strchr(buf, '\'');
    }
    else
    {
        delim = strchr(buf, ' ');
    }

    while (delim)
    {
        argv[argc++] = buf;
        *delim = '\0';
        buf = delim + 1;
        while (*buf && (*buf == ' ')) /* ignore spaces */
            buf++;

        if (*buf == '\'')
        {
            buf++;
            delim = strchr(buf, '\'');
        }
        else
        {
            delim = strchr(buf, ' ');
        }
    }
    argv[argc] = NULL;

    if (argc == 0) /* ignore blank line */
        return 1;

    /* should the job run in the background? */
    if ((bg = (*argv[argc - 1] == '&')) != 0)
    {
        argv[--argc] = NULL;
    }
    return bg;
}

/*
 * builtin_cmd - If the user has typed a built-in command then execute
 *    it immediately.
 */
int builtin_cmd(char **argv)
{
    if (!strcmp(argv[0], "quit")) // 如果命令是quit，退出
    {
        for (int i = 0; i < MAXJOBS; i++)
        {
            if (jobs[i].pid != 0)
            {
                if (kill(-jobs[i].pid, SIGKILL) < 0)
                    unix_error("kill (sigint) error");
            }
        }
        exit(0);
    }
    else if (!strcmp(argv[0], "bg") || !strcmp(argv[0], "fg")) // 如果是bg或者fg命令，执行do_fgbg函数
        do_bgfg(argv);
    else if (!strcmp(argv[0], "jobs")) // 如果命令是jobs，列出正在运行和停止的后台作业
        listjobs(jobs);
    else
        return 0; /* 不是内置命令，以0返回eval */
    return 1;
}

/*
 * do_bgfg - Execute the builtin bg and fg commands
 */
void do_bgfg(char **argv)
{
    int num;
    struct job_t *job;
    // 没有参数的fg/bg不符合规定
    if (!argv[1])
    { // 命令行为空
        signal_safe_print("%s command requires PID or %%jobid argument\n", argv[0]);
        return;
    }
    // 检测fg/bg参数。
    if (argv[1][0] == '%')
    {
        if ((num = strtol(&argv[1][1], NULL, 10)) <= 0) // 获取jid
        {
            signal_safe_print("%s: argument must be a PID or %%jobid\n", argv[0]); // 失败,打印错误消息
            return;
        }
        if ((job = getjobjid(jobs, num)) == NULL) // 根据jid获取job
        {
            signal_safe_print("%%%d: No such job\n", num); // 没找到对应的job
            return;
        }
    }
    else
    {
        if ((num = strtol(argv[1], NULL, 10)) <= 0) // 获取PID
        {
            signal_safe_print("%s: argument must be a PID or %%jobid\n", argv[0]); // 失败,打印错误消息
            return;
        }
        if ((job = getjobpid(jobs, num)) == NULL) // 根据PID获取job
        {
            signal_safe_print("(%d): No such process\n", num); // 没找到对应的进程
            return;
        }
    }

    if (!strcmp(argv[0], "bg")) // 该进程需要在后台运行
    {
        // bg会启动子进程，并将其放置于后台执行
        job->state = BG; // 设置状态BG
        if (kill(-job->pid, SIGCONT) < 0)
            unix_error("kill error");
        signal_safe_print("[%d] (%d) %s", job->jid, job->pid, job->cmdline);
    }
    else if (!strcmp(argv[0], "fg")) // 该进程需要在前台运行
    {
        job->state = FG; // 设置状态FG
        if (kill(-job->pid, SIGCONT) < 0)
            unix_error("kill error");
        // 当一个进程被设置为前台执行时，当前tsh应该等待该子进程结束
        waitfg(job->pid);
    }
    else // 指令出现异常
    {
        puts("do_bgfg error");
        exit(0);
    }
    return;
}

/*
 * waitfg - Block until process pid is no longer the foreground process
 */
void waitfg(pid_t pid)
{
    struct job_t *job = getjobpid(jobs, pid);
    if (!job)
        return;
    // 新设立一个wait信号集
    sigset_t wait;
    if (sigemptyset(&wait) < 0) // 初始化wait信号集.
        unix_error("Error wait:initialize error.");
    //   如果当前子进程的状态没有发生改变，则tsh继续休眠
    int tempstate = job->state;
    int temppid = job->pid;
    while (job->state == FG)
        sigsuspend(&wait); // 使用空信号集替换信号掩码，即信号掩码为空，此时任何信号都会唤醒该进程
    if (job->state != tempstate && job->state != FG && verbose)
    {
        signal_safe_print("waitfg:Process (%d) no longer the fg process\n", temppid);
    }
    return;
}

/*****************
 * Signal handlers
 *****************/

/*
 * sigchld_handler - The kernel sends a SIGCHLD to the shell whenever
 *     a child job terminates (becomes a zombie), or stops because it
 *     received a SIGSTOP or SIGTSTP signal. The handler reaps all
 *     available zombie children, but doesn't wait for any other
 *     currently running children to terminate.
 */
void sigchld_handler(int sig)
{
    int status, jid;
    pid_t pid;
    struct job_t *job;

    if (verbose)
        puts("sigchld_handler: entering");

    while ((pid = waitpid(-1, &status, WNOHANG | WUNTRACED)) > 0) // 以非阻塞方式等待所有子进程
    // 避免使用信号计数
    {

        // pid删除混乱错误
        if ((job = getjobpid(jobs, pid)) == NULL)
        {
            signal_safe_print("Error deleting of (%d)\n", pid);
            return;
        }

        jid = job->jid;

        //  收到挂起指令
        if (WIFSTOPPED(status))
        {
            signal_safe_print("Job [%d] (%d) stopped by signal %d\n", jid, job->pid, WSTOPSIG(status));
            job->state = ST; // 状态设为挂起
        }

        // 退出指令
        else if (WIFEXITED(status))
        {
            if (deletejob(jobs, pid))
                if (verbose)
                {
                    signal_safe_print("sigchld_handler: Job [%d] (%d) deleted\n", jid, pid);
                    signal_safe_print("sigchld_handler: Job [%d] (%d) terminates OK (status %d)\n", jid, pid, WEXITSTATUS(status));
                }
        }
        // 未捕获信号终止
        else
        {
            if (deletejob(jobs, pid)) // 清除进程
            {
                if (verbose)
                    signal_safe_print("sigchld_handler: Job [%d] (%d) deleted\n", jid, pid);
            }
            signal_safe_print("Job [%d] (%d) terminated by signal %d\n", jid, pid, WTERMSIG(status));
        }
    }

    if (verbose)
        puts("sigchld_handler: exiting");

    return;
}

/*
 * sigint_handler - The kernel sends a SIGINT to the shell whenver the
 *    user types ctrl-c at the keyboard.  Catch it and send it along
 *    to the foreground job.
 */
void sigint_handler(int sig)
{
    if (verbose)
        puts("sigint_handler: entering");
    pid_t pid = fgpid(jobs); // 获取前台进程的pid
    if (pid)
    {
        // 发送SIGINT给前台进程组里的所有进程
        if (kill(-pid, SIGINT) < 0)
            unix_error("kill (sigint) error");
        if (verbose)
        {
            signal_safe_print("sigint_handler: Job (%d) killed\n", pid);
        }
    }
    if (verbose)
        puts("sigint_handler: exiting");
    return;
}

/*
 * sigtstp_handler - The kernel sends a SIGTSTP to the shell whenever
 *     the user types ctrl-z at the keyboard. Catch it and suspend the
 *     foreground job by sending it a SIGTSTP.
 */
void sigtstp_handler(int sig)
{
    if (verbose)
        puts("sigstp_handler: entering");

    pid_t pid = fgpid(jobs);
    struct job_t *job = getjobpid(jobs, pid);

    if (pid)

        if (kill(-pid, SIGTSTP) < 0) // 该进程挂起
            unix_error("kill (tstp) error");
    if (verbose)
    {
        signal_safe_print("sigstp_handler: Job [%d] (%d) stopped\n", job->jid, pid);
    }

    if (verbose)
        puts("sigstp_handler: exiting");
    return;
}

/*********************
 * End signal handlers
 *********************/

/***********************************************
 * Helper routines that manipulate the job list
 **********************************************/

/* clearjob - Clear the entries in a job struct */
void clearjob(struct job_t *job)
{
    job->pid = 0;
    job->jid = 0;
    job->state = UNDEF;
    job->cmdline[0] = '\0';
}

/* initjobs - Initialize the job list */
void initjobs(struct job_t *jobs)
{
    int i;

    for (i = 0; i < MAXJOBS; i++)
        clearjob(&jobs[i]);
}

/* maxjid - Returns largest allocated job ID */
int maxjid(struct job_t *jobs)
{
    int i, max = 0;

    for (i = 0; i < MAXJOBS; i++)
        if (jobs[i].jid > max)
            max = jobs[i].jid;
    return max;
}

/* addjob - Add a job to the job list */
int addjob(struct job_t *jobs, pid_t pid, int state, char *cmdline)
{
    int i;

    if (pid < 1)
        return 0;

    for (i = 0; i < MAXJOBS; i++)
    {
        if (jobs[i].pid == 0)
        {
            jobs[i].pid = pid;
            jobs[i].state = state;
            jobs[i].jid = nextjid++;
            if (nextjid > MAXJOBS)
                nextjid = 1;
            strcpy(jobs[i].cmdline, cmdline);
            if (verbose)
            {
                signal_safe_print("Added job [%d] %d %s\n", jobs[i].jid, jobs[i].pid, jobs[i].cmdline);
            }
            return 1;
        }
    }
    signal_safe_print("Tried to create too many jobs\n");
    return 0;
}

/* deletejob - Delete a job whose PID=pid from the job list */
int deletejob(struct job_t *jobs, pid_t pid)
{
    int i;

    if (pid < 1)
        return 0;

    for (i = 0; i < MAXJOBS; i++)
    {
        if (jobs[i].pid == pid)
        {
            clearjob(&jobs[i]);
            nextjid = maxjid(jobs) + 1;
            return 1;
        }
    }
    return 0;
}

/* fgpid - Return PID of current foreground job, 0 if no such job */
pid_t fgpid(struct job_t *jobs)
{
    int i;

    for (i = 0; i < MAXJOBS; i++)
        if (jobs[i].state == FG)
            return jobs[i].pid;
    return 0;
}

/* getjobpid  - Find a job (by PID) on the job list */
struct job_t *getjobpid(struct job_t *jobs, pid_t pid)
{
    int i;

    if (pid < 1)
        return NULL;
    for (i = 0; i < MAXJOBS; i++)
        if (jobs[i].pid == pid)
            return &jobs[i];
    return NULL;
}

/* getjobjid  - Find a job (by JID) on the job list */
struct job_t *getjobjid(struct job_t *jobs, int jid)
{
    int i;

    if (jid < 1)
        return NULL;
    for (i = 0; i < MAXJOBS; i++)
        if (jobs[i].jid == jid)
            return &jobs[i];
    return NULL;
}

/* pid2jid - Map process ID to job ID */
int pid2jid(pid_t pid)
{
    int i;

    if (pid < 1)
        return 0;
    for (i = 0; i < MAXJOBS; i++)
        if (jobs[i].pid == pid)
        {
            return jobs[i].jid;
        }
    return 0;
}

/* listjobs - Print the job list */
void listjobs(struct job_t *jobs)
{
    int i;

    for (i = 0; i < MAXJOBS; i++)
    {
        if (jobs[i].pid != 0)
        {
            signal_safe_print("[%d] (%d) ", jobs[i].jid, jobs[i].pid);
            switch (jobs[i].state)
            {
            case BG:
                signal_safe_print("Running ");
                break;
            case FG:
                signal_safe_print("Foreground ");
                break;
            case ST:
                signal_safe_print("Stopped ");
                break;
            default:
                signal_safe_print("listjobs: Internal error: job[%d].state=%d ",
                                  i, jobs[i].state);
            }
            signal_safe_print("%s", jobs[i].cmdline);
        }
    }
}
/******************************
 * end job list helper routines
 ******************************/

/***********************
 * Other helper routines
 ***********************/

/*
 * usage - print a help message
 */
void usage(void)
{
    signal_safe_print("Usage: shell [-hvp]\n");
    signal_safe_print("   -h   print this message\n");
    signal_safe_print("   -v   print additional diagnostic information\n");
    signal_safe_print("   -p   do not emit a command prompt\n");
    exit(1);
}

/*
 * unix_error - unix-style error routine
 */
void unix_error(char *msg)
{
    signal_safe_print("%s: %s\n", msg, strerror(errno));
    exit(1);
}

/*
 * app_error - application-style error routine
 */
void app_error(char *msg)
{
    fprintf(stdout, "%s\n", msg);
    exit(1);
}

/*
 * Signal - wrapper for the sigaction function
 */
handler_t *Signal(int signum, handler_t *handler)
{
    struct sigaction action, old_action;
    action.sa_handler = handler;
    sigemptyset(&action.sa_mask); /* block sigs of type being handled */
    action.sa_flags = SA_RESTART; /* restart syscalls if possible */
    if (sigaction(signum, &action, &old_action) < 0)
        unix_error("Signal error");
    return (old_action.sa_handler);
}

/*
 * sigquit_handler - The driver program can gracefully terminate the
 *    child shell by sending it a SIGQUIT signal.
 */
void sigquit_handler(int sig)
{
    signal_safe_print("Terminating after receipt of SIGQUIT signal\n");
    exit(1);
}
